ABB Switzerland Ltd REG 316*4 1MRB520049-Uen / Rev. C
2-6
2.3. Auxiliary supply unit
The auxiliary supply unit 316NG65 derives all the supply volt-
ages the protection requires from the station battery. Capacitors
are provided which are capable of bridging short interruptions
(max. 50 ms) of the input voltage. The auxiliary supply unit is
protected against changes of polarity.
In the event of loss of auxiliary supply, the auxiliary supply unit
also generates all the control signals such as re-initialisation and
blocking signals needed by all the other units.
The technical data of the auxiliary supply unit are to be found in
the data sheet.
2.4. Input transformer unit
The input transformer unit 316GW61 serves as input interface
between the analogue primary system variables such as cur-
rents and voltages and the protection. The mounting plate of the
unit can accommodate up to nine c.t's and v.t's. The shunts
across the secondaries of the c.t's are also mounted in the input
transformer unit.
The input transformers provide DC isolation between the primary
system and the electronic circuits and also reduce (in the case of
the c.t's, with the aid of a shunt) the voltage and current signals
to a suitable level for processing by the A/D converters. Thus the
input transformer unit produces voltage signals at its outputs for
both current and voltage channels.
The c.t's and v.t's actually fitted in the input transformer unit vary
according to version. Further information can be obtained from
the data sheet.
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